In a communication system, in order to decrease network construction and operation costs, a traditional drive test is: using manual labor to test an area required to be monitored and optimized.
Based on the evolution of the next generation network, on one hand, in order to reduce the dependence on the traditional drive test, on the other hand, in order to enable a test result of a User Equipment (UE) to be used for optimizing the network automatically and understanding an operating condition of the network comprehensively, a technical research of MDT is proposed in the LTE system. The MDT technology also can be applied in the UMTS. The implementation mode of the MDT technology is based on an eNB sending measurement control and report mechanism to the UE and the UE reporting after the measurement. FIG. 1 is a schematic diagram of an application framework of the existing MDT in the UMTS, and as shown in FIG. 1, a network side and a terminal device are included, wherein, the network side includes a Radio Access Network (RAN) side device and a network management system. The report mechanism includes three types, i.e. real-time reporting in connection state, log reporting in IDLE state and log reporting in connection state.
Currently, the measurement contents of the MDT mainly include the following kinds.
1) Periodical downlink pilot measurement: namely, radio environment measurement, such as a periodical record on Common Pilot Channel Received Signal Code Power (CPICH RSCP), CPICH Energy per chip to noise power density (CPICH Ec/No), Reference Signal Received Power (RSRP) and Reference Signal Received Quality (RSRQ) (only in connection mode). This measurement log corresponds to the user example “Coverage Optimization”.
Operators realize that main measurements of the downlink (DL) coverage or achievable throughput are common pilot receiving grade and Signal to Interference Ratio (SIR) grade. A configuration for the existing Radio Resource Management (RRM) measurement is mainly dependent on a measurement report and periodical report of event trigger. Some restrictions also exist as below.
a) There is no accompanying location information. Even though the operators can use the DL coverage to distinguish a cell, the operators still need to determine an area having the problem in the cell by executing a drive test, for the accurate location information can be detected by the low common pilot receiving grade/SIR grade, and can not be obtained from the current RRM mechanism.
b) The existing RRM mechanism only allows to make the measurement report when the UE has been connected to a specific cell and there is sufficient uplink (UL) coverage for transmitting the measurement report. This will limit the measurements collected from the UE, and the UE can not experience a Reliable Linked Frame (RLF) and sufficient UL coverage.
2) Serving Cell signal becomes worse than threshold: that is, when measurement of the serving cell is less than the configured threshold, the radio environment measurement is recorded, such as CPICH RSCP, CPICH Ec/No, or Time Division Duplex Primary CPICH RSCP (TDD P-CCPCH RSCP) and Interference Signal Code Power (ISCP), RSRP and RSRQ (only in connection mode). A measurement log window is required, and the object is to collect information in a certain period of time before and after the event occurs. The measurement log corresponds to the user example “Coverage Optimization”.
If the operators are interested in a specific DL coverage problem, the measurement log corresponding to the interested problem is effective. In order to find out the area in problem, the operators can transform their standards (e.g. outside the coverage) into a threshold. In order to distinguish a characteristic of the problem (e.g. occurred in a specific mobile scenario), the measurement content is the useful measurement log provision information.
3) Transmit power headroom becomes less than threshold: that is, when the transmit power headroom of the UE is less than the configured threshold, the transmit power headroom and radio environment measurement such as CPICH RSCP, CPICH Ec/No, or TDD P-CCPCH RSCP and ISCP, RSRP and RSRQ (only in connection mode) are recorded. The measurement log corresponds to the user example “Coverage Optimization”.
The operators can detect that there is no sufficient UL link budget by observing a UL transmit power grade, and also can infer the achievable UL throughput grade in the network. Collecting such information can help the operators adjust Cell Individual Offset (CIO) better to determine a layout of the cell in the network center and adjust the antenna tilt angle and so on.
4) Random access failure: that is, when the random access failure occurs, the detail information about the random access and the radio environment measurement such as CPICH RSCP, CPICH Ec/No, or TDD P-CCPCH RSCP and ISCP, RSRP and RSRQ (only in connection state) are recorded. The measurement log corresponds to the user example “Coverage Optimization”.
The reason of the random access failure is, for example, an inaccurate transmitting power setup or competition and so on. The operators can collect the information about the random access failure to analyze the characteristics of the random access failure. A DL radio environment measurement is also necessary, such as the measurement of CPICH RSCP, CPICH Ec/No, RSRP and RSRQ, for the open loop power control in random access process relies on these characteristics. Collecting such information can help the operators adjust random access parameters and the antenna tilt angle and so on.
5) Paging Channel failure: that is, when the UE does not decode a PCCH in a paging channel within the continuous time of X2, the detail information such as location information, time and cell identification of radio environment is recorded (even though the operators can decode a PDCCH during the paging). The measurement log corresponds to the user example “Common Channel Parameterization”.
In the IDLE mode, for the operators, whether the UE can be paged reliably is extremely important. If one user can not be paged reliably, it will have a negative influence on the user experience (at least in a paging unit), and also have an influence on incomes of the operators (for call opportunities becomes less). In the current network, the drive test can be used to estimate the ability of the UE by receiving paging message within the cell coverage area. Since these actions will cause high costs, if the UE can record the occurrence time in which the UE can not decode the information on the paging channel and other related information, it will be very beneficial.
6) Broadcast Channel failure: that is, when the UE does not read a related DL common channel to obtain the required system message for residing in one cell, message information such as location information, time, cell identification and frequency of radio environment is recorded. The measurement corresponds to the user examples “Coverage and Capacity Optimization” and “Common Channel Parameterization”.
7) Radio Link failure report: that is, when the UE has the RLF, the UE reports a radio measurement, such as CPICH RSCP, CPICH Ec/No, or TDD P-CCPCH RSCP and ISCP, RSRP and RSRQ. The measurement of RLF Report corresponds to the user example “Coverage Optimization”.
The RLF Report can distinguish several problems from the coverage aspects. Therefore, in a realistic network, it is expected that the probability of detecting the coverage holes through the RLF Report measurement information can be high. In addition, some problems generally related to the detection for the DL common channel are also resulted from the coverage problem. The RLF Report provides a method for solving a basic DL coverage problem, and specific measurements of the common channel parameterization can concentrate on adjusting common channel parameters.
Collecting the measurement information of measurement contents of the above MDT can help the operators find out the coverage problems in the specific area and minimize the manual drive test.
Meanwhile, service continuity for mobile users is a basic function of a cellular mobile communication system, and the handover of the serving cells of the mobile station is a main measure for guaranteeing the service continuity. In order to facilitate the handover of the user equipment, the system needs to configure an adjacency relation for each cell, such that the network side informs the user equipment of neighbor cell information, the user equipment reports a measurement result after measuring the neighbor cell, and the network side indicates the user equipment to switch to a certain neighbor cell according to the reported measurement result.
Which neighbor cells around that a certain cell has is not only related to the cell distance, but also closely related to the radio environment in which the cell is located. For the radio environment, especially an urban area environment which has concentrated high-rise buildings, is intricate and complicated, it is difficult to precisely judge which cell should be configured to which neighbor cells in the preliminary stage of the network plan. Moreover, some situations such as newly adding one cell or cell attribute change in the system but not updating a neighboring relation of the cell in time, or environmental change and omission of network plan staff, all will cause that the neighbor cell information is not updated in time. Therefore, the user equipment can not be switched to other cells in time, such that the load of the current cell is excessively heavy, the signal quality of the current cell becomes worse, and the situation of serious interference or user call drop occurs.
However, the MDT technology mentioned previously can fully use the measurement of the UE to collect and report the situations of surrounding radio environments. Currently, no effective measuring method has been provided to enable the UE to obtain the surrounding neighbor cell information and report.